Location sensor having a satellite receiver for position determination

ABSTRACT

A location sensor in which a satellite receiver, a rotation rate sensor constituting a direction sensor, and an acceleration sensor constituting a displacement sensor are arranged in a housing. The signals of these sensors are conveyed to a common filter, so that the location, the movement velocity, and/or the movement direction can be picked off at the output of the location sensor. The compact arrangement of the individual sensors makes possible multiple utilization of individual components, for example of filters.

FIELD OF THE INVENTION

The present invention is based on a location sensor having a satellitereceiver for position determination.

BACKGROUND INFORMATION

It is known to use a location and navigation system for determininglocation, in particular of a motor vehicle. Sensors for determiningdirection of travel and distance traveled are often connected to thenavigation system. To determine an absolute position of the motorvehicle, it is also possible to use a satellite receiver as known, forexample, by way of the Global Positioning System (GPS).

Installation of the direction and displacement sensors on the motorvehicle is, however, relatively complex. On the other hand, positiondetermination using the GPS receiver is relatively imprecise, so that ina densely packed network of streets an accurate location cannot alwaysbe determined. In addition, in built-up urban areas it is not possibleto receive enough GPS satellites, so that location determination basedon satellite reception is not always satisfactory. Moreover, both thesignals of both the satellite receiver and the direction anddisplacement sensors must be processed using corresponding filters, sothat location determination is not only unreliable but also complex.

SUMMARY OF THE INVENTION

The location sensor according to the present invention has, in contrastthereto, the advantage that because the sensors are arranged in the samehousing, the location sensor can be of very compact configuration. Thisadvantageously decreases not only assembly effort, but alsomanufacturing costs. It is particularly advantageous that because of thecompact design, individual components for signal analysis, for examplefilters, can be used in multiple fashion, so that the production outlayfor the location sensor is further reduced. As a result of thecompatible data format at the output of the location sensor, it is alsopossible to replace conventional satellite receivers.

The features set forth in the dependent claims make possibleadvantageous developments of and improvements to the location sensor. Itis particularly advantageous that a GPS and/or GLONASS system is used asthe satellite receiver, since these systems are already installed and tosome extent are authorized for civilian use.

The use of one or more acceleration sensors and/or a rotation ratesensor (gyro sensor) as displacement or direction sensors appearsfavorable because these sensors can be installed, independently ofsignal transducers of the motor vehicle, in the housing of the locationsensor. Additional external vehicle installations and connectors canthereby be eliminated.

The additional use of a barometric altimeter or a temperature sensormeans that the accuracy of the position determination can be monitoredand improved. Since an altitude determination is also possible whenenough GPS satellites are being received, comparison with the readingsof the barometric altimeter makes it possible to calibrate the positiondetermination. Since the working accuracy of the components used alsodepends on ambient temperature, these errors can advantageously becompensated for with the aid of the temperature sensor.

To allow a position determination or in order to calibrate the sensors,for example of the acceleration sensor, even when reception conditionsfor the sensor signals are very unfavorable, it is advantageous toprovide for the connection of a speed transducer. The speed transducercan be a signal transducer, present on the vehicle, for a distancetraveled, the signals of which are additionally usable for calibrationof the acceleration sensor.

Connecting the individual sensors together to a common position filterallows the elimination of further subassemblies which would otherwise benecessary for each individual sensor. It is particularly favorable inthis context that the sensor signals are weighted with a priority factorso that, for example, the position determination with the GPS receiverpossesses the highest priority as long as enough satellite signals arereceivable. If, on the other hand, satellite signals are no longerreceivable, for example in a tunnel, the displacement sensor and thedirection sensor receive the highest priority. These priorities are thenmaintained until the satellite signals are once again receivable withsufficient quality.

It is particularly advantageous that a Kalman filter is provided as theposition filter. In this filter the errors of the individual sensorscompensate for one another, thus improving the location result.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a block diagram of a conventional location and navigationsystem.

FIG. 2 shows an exemplary embodiment of a location sensor according tothe present invention.

DETAILED DESCRIPTION

FIG. 1 shows a conventional location system that is configured with aGPS receiver 1, a magnetic compass 3 as direction sensor, and adisplacement sensor 4, for example with wheel sensors on a motorvehicle. GPS receiver 1 has a position filter 6 for determining locationfrom the received satellite signals. The signals of these sensors areconnected to a computer 5, at whose output 9 the position or locationdata can be picked off.

GPS receiver 1 as well as the individual sensors 3, 4 and computer 5 areinstalled in different housings, the individual housings being attachedat respectively suitable points on the motor vehicle.

FIG. 2 shows an exemplary embodiment according to the present inventionof a location sensor 10 in whose housing 11 satellite receiver 1 isarranged, with direction sensor 3 and displacement sensor 4, as acompact unit. The displacement sensor is configured, for example, as anintegrating rotation rate sensor (gyro sensor). The gyro sensor is knownper se, and therefore needs no further explanation. What is provided asdisplacement sensor 4 is an acceleration sensor from whose signals adistance traveled can be calculated by integration. The outputs of thesesensors are switched to a position filter 6. Position filter 6 ispreferably configured as a Kalman filter.

To further improve the availability of the position data, a temperaturesensor 12 and/or a barometric altimeter 7 can be provided. Their outputsare also connected to position filter 6. In a further embodiment of thepresent invention, a speed transducer 14 is provided as the displacementsensor; its signals are also conveyed via an external connection toposition filter 6. Additionally, an antenna 2 is provided for satellitereceiver 1. Position filter 6 calculates, from the signals of theindividual sensors, the instantaneous vehicle position, direction oftravel, and distance traveled, and makes these data available in acompatible data format at an output 9.

The Kalman filter is a optimum filter that supplies, from the systemdynamics, the stochastic parameters of the process and measurementnoise, and an initial datum, an estimate of the system status at minimumestimation error. A detailed description may be found in Robert GroverBrown, Patrick Y. C. Hwang, “Introduction to Random Signals and AppliedFiltering,” John Wiley & Sons, Inc., New York, 1992.

The manner of operation of this arrangement will now be explained inmore detail. Position filter 6 is designed so that it processes thesignals of all the sensors and signal transducers connected to it. It isconfigured as a Kalman filter, and can compensate for the individualerrored signals of the sensors connected to it, so that an actuallocated position is output with the greatest possible probability.

Since both the signals of satellite receiver 1 and the signals ofdirection and travel sensors 3, 4 are errored (and the errors ofdirection and travel sensors 3, 4 tend in particular to accumulate), aneffort is made with the aid of the arrangement according to the presentinvention to minimize the errors in order to determine a maximallyreliable located position. According to the present invention, thesignals of the individual components are weighted with a priorityfactor. The weighted signals can then be analyzed according to the rulesof dead-reckoning navigation. For example, if enough GPS satellites arereceivable, the position determination of satellite receiver 1 thenreceives the highest priority, for example a factor of 1, whiledirection sensor 3 and displacement sensor 4 receive a factor of 0. Ifsatellite reception is impeded under poor reception conditions, forexample in built-up urban areas or in a tunnel, GPS receiver 1 thenreceives the lowest priority factor, e.g. 0. Since position filter 6 iscontinuously feeding back and comparing the position data obtained fromgyro sensor 3 and acceleration sensor 4, concurrently with the positiondata of satellite receiver 1, the vehicle position can thus beascertained even if no GPS signals are available. In this case gyrosensor 3 and acceleration sensor 4 receive the highest priority, e.g. avalue of 1. As soon as enough satellites are once again receivable, thelast position is compared to the position determined by satellitereceiver 1 and corrected if necessary. This weighting of the priorityfactor as a function of reception quality results in a highly accuratelocated position. The individual sensors 3, 4 thus monitor one another,so that not as much individual importance is placed on the accuracy ofthe individual sensor itself. Since gyro sensor 3 and accelerationsensor 4 are used only for a limited distance, the accumulated errors ofthese sensors are advantageously also limited. A somewhat moreinaccurate and therefore more economical consumer-grade gyro sensor canthen be used as the gyro sensor, since its data are weighted only if themore precise measured data of GPS receiver 1 are not available forcalculating the position data.

The use of temperature sensor 12 and/or barometric altimeter 7 allows afurther optimization of the located position.

In a further embodiment of the present invention, provision is made alsoto use the signal of speed transducer 14 as a displacement sensor. Whenan acceleration sensor 4 is used, provision is made to sense theacceleration in the three mutually perpendicular spatial axes so as toderive the displacement and direction information directly from thecomplex acceleration vector. In this case, the use of a gyro sensor togenerate the direction information can be dispensed with.

If gyro sensor 3 and acceleration sensor 4 are embodied as amicromechanical component, preferably on a semiconductor chip, they canthen be implemented as an integrated circuit or as a module on a circuitboard, in a highly space-saving manner.

The compatible data output format yields the advantage that an existingGPS receiver 1 can be replaced, without additional outlay, with locationsensor 10 according to the present invention.

What is claimed is:
 1. A location sensor for a position determination,comprising: a satellite receiver including a position filter; adirection sensor having a first output signal; a displacement sensorhaving a second output signal, the first and second output signals beingswitched to the position filter; a housing accommodating the satellitereceiver, the direction sensor and the displacement sensor; and acomputing arrangement including an output arrangement, the computingarrangement weighting the first output signal, the second output signaland a third output signal of the satellite receiver as a function of apriority factor, the priority factor being weighted as a function of anavailability of the first, second and third output signals, thecomputing arrangement providing data which is indicative of at least oneof a location, a movement velocity, and a movement direction, the databeing provided to the output arrangement and picked off in a compatibledata format.
 2. The location sensor according to claim 1, wherein thesatellite receiver receives at least one signal from at least one of aGPS satellite and a GLONASS satellite.
 3. The location sensor accordingto claim 1, wherein the displacement sensor includes an accelerationsensor.
 4. The location sensor according to claim 3, wherein theacceleration sensor determines accelerations in three axes.
 5. Thelocation sensor according to claim 1, wherein the direction sensorincludes at least one of a rotation rate sensor and a gyro sensor. 6.The location sensor according to claim 1, further comprising: abarometric altimeter situated in the housing, a barometric output of thebarometric altimeter being connected to the position filter.
 7. Thelocation sensor according to claim 1, further comprising: a temperaturesensor situated in the housing, a temperature output of the temperaturesensor being connected to the position filter.
 8. The location sensoraccording to claim 1, further comprising: an external sensor connectingto the housing, signals of the external sensor being provided, via anexternal connection, to the position filter.
 9. The location sensoraccording to claim 8, wherein the external sensor includes a speedtransducer.
 10. The location sensor according to claim 1, wherein theposition filter includes a Kalman filter.
 11. The location sensoraccording to claim 1, wherein the location sensor is a part of anavigation system.
 12. The location sensor according to claim 11,wherein a motor vehicle includes the navigation system.